Add release appxmanifest (#1682)

Currently, the copy of Package.appxmanifest in this repo is overwritten with a copy from an internal repo during release builds. This change adds the release version of Package.appxmanifest to this repo, to make it easier to maintain and keep it in sync with the copy used during development.

build/pipelines/azure-pipelines.release.yaml

@@ -20,17 +20,20 @@ jobs:
   parameters:
     platform: x64
     isReleaseBuild: true
+    useReleaseAppxmanifest: true
 
 - template: ./templates/build-single-architecture.yaml
   parameters:
     platform: x86
     isReleaseBuild: true
+    useReleaseAppxmanifest: true
     condition: not(eq(variables['Build.Reason'], 'PullRequest'))
 
 - template: ./templates/build-single-architecture.yaml
   parameters:
     platform: ARM
     isReleaseBuild: true
+    useReleaseAppxmanifest: true
     condition: not(eq(variables['Build.Reason'], 'PullRequest'))
 
 - template: ./templates/run-unit-tests.yaml